Put a sign(A comedical one found off the internet) saying,"Don't enter, I'm masturbating" or something along those lines.
If they think it's a joke and play along, they won't go in. If they are party poopers, they realize they ****** up.

You can't just sit him down and say something like... "Dad, I hate that you won't let me be alone. I feel like you can't trust me. That makes it hard for me to trust you, and if I can't trust my own father, who can I trust?"

Maybe he has some reason buried in his past that makes him concerned for your own well-being. I wish I could give more ideas other than just talking it out, but honestly, I can't see any other method working.

Every since childhood I've been his precious lil golden child, now he hates how I don't like to talk to him, even though he only gives me reasons not to. He hates seeing me do unproductive things. Once I was playing CoD zombies after school and he told me to shut it off, I said, ok let me just tell my friends I have to end the game. Then he took an hatchet off the wall and started hacking my night stand table thing into pieces.

He was always like this, just never to me in the past, and NEVER in public.

He once slapped my sister and held her up to the wall by her neck for some reason.
He threw french fries at her door for not wanted food.

and when I was about 15.5 he wanted to hit my best friend, (cat) and he grabbed him so I held onto his arms so he picked me up by the neck and held me to the side of my bad and screamed don't put your hands on me lke that or i'll punch out your teeth or some **** .

I'll be honest. I don't care how long it's been since he flipped. You should go get some help. Don't even tell yourself any **** about "Oh, he's my dad, I can't do anything to my dad." or "What if he hurts me?" Just freaking get some help before things get really bad. I know that this is funnyjunk, and that personal problems are best kept to one's self, but good grief, you need to do something about that.

And I apologize for making the generalization that you're living in the US. You might not be, but honestly, if you've got access to the net, and something to play games on, you're probably not living in total poverty.

******* just do it! I swear to every god that's ever been conceived, if you don't, then it's not going to ever get better.

Yeah, sure. You'll move out eventually, but what's to stop him from visiting all the time and butting in on your life? Then you meet a nice girl, want to have kids. Before you know it, he's butting in on his grandchildren's lives, or worse, you start to butt in on your own kids lives.

Don't let that ******* happen. Don't pass on the imperfections of your parents to your own kids. This isn't some third world country where there's nothing you can do. You said yourself that he's attacked not only you, but your sister and your friend. Do you really want him to attack more people just because you're too scared to do anything about it?

But everything just feels so normal when he's fine, he just came into my room and gave me two cookies with fluff between them. And I'm sure he won't butt in on my life, They don't care when I'm making something to eat, or doing 1 hours of homework, or looking at funny internet videos, He ignores me in said events, He only cares about door blockage, and me preventing cat slapping I think.

I've let many opportunities pass me by, and I'm just naturally afraid of things I guess.

Yeah, I read that. It's still no excuse. See? You're rationalizing his anger because it was directed at an animal, and not a person. Look, I've tried to let you know that you need to do something about it, but if you're not going to do it, then maybe talk to a friend about it. Maybe your family would be too scared to say anything about it, but a friend would gladly say something if they were truly your friend. That's all I'm going to say, as I'm sure OP is upset about this much space being taken for a discussion about an abusive parent. I hope everything works out for you, and I sincerely hope you decide to take the initiative and do something about it, rather than making yourself a victim.

one time just start doing it in front of the door (as if it were your audience) then if you hear the handle turning just close your eyes and imagine Alexis Texas walking through that door, finish, they'll never bother you again. (probably because they'd kill you)

Oh man, I had it bad when I was growing up. My parents were really over protective in terms of my access to technology. I couldn't get any gaming consoles (Xbox, Gamecube, Playstation) or anything handheld like a GBA. Hell, I got my first phone in Freshman year. We had a family computer in our house but when I was younger it was always monitored. We weren't allowed to use it unless a parent was with us. In 7th or 8th grade they lifted that ban but still limited what we were allowed to use the computer for. I remember once I went to Weird Al Yankovik's website to hear a song, after my friend gave me a c-d with some of his music on it. The next day I got grounded because apparently my father would check the computers history daily using some program he got from his office. I couldn't watch movies that were over PG-13 until I was in Highschool. It was pretty rough growing up like that but luckily I had a friend who always allowed me to use his stuff at his house. Thanks to him I grew up with Warrio Land 4 and pretty much constant Smash Bros.......although I did miss out on Pokémon and a lot of the other basics like Halo and MoH. Also, my younger brother had it completely differently. He had his own computer by 6th grade and was playing any games he wanted by 7th. Sucks to be first born, doesn't it?

sometimes, i get sad because i feel like the only adult in a funnyjunk of teenagers. but then i see the angsty posts and either laugh at how spoiled kids are, or remember how good i have it now and everything is okay. thank you, funnyjunk.

That's invasion of privacy right there. We had a guy stay at our house once, and he asked if he could use my cell for a bit. He was a jerk and used about 30 texts or so on his girlfriend. He didn't delete them. He's still a douche, but I didn't go through his texts cause that's private stuff.

Joke's on them.
I have 3 batteries and my charging port is broken, so I have to take the batteries out and charge them inside a universal phone battery charger.
My phone is NEVER turned off and NEVER out of my reach because of this.